The invention relates to an internal combustion engine. In known internal combustion engines of a similar type, when they are operated with a fuel-air mixture which must be externally ignited, the disadvantage arises that this mixture ignites poorly, especially when it is kept lean in fuel. This causes a nonuniform torque output of the engine. Various attempts have been made to attain a sufficiently positive ignition and reaction of the fuel and air with each other while keeping the proportion of fuel as low as possible, with the intention being to attain a mixture enrichment near the ignition point in the ignition chamber by means of stratification. Beyond this, raising the temperature level in the ignition chamber permits an increase in the ignitability of the lean fuel-air mixture. However, the occurrence of spontaneous ignition and premature wear because of overly high temperatures must be avoided.
In a known apparatus, the temperature of the ignition chamber wall was controlled with this purpose in mind. This is accomplished by using a thermal pipe surrounding the ignition chamber which, so long as the ignition chamber is cold, prevents the immediate conduction of the head produced there away to the cooled chambers of the internal combustion engine and assures that an increased heat conduction to the cooled walls of the internal combustion engine only appears at high temperatures which can be set as needed.
In this known apparatus, it was further proposed to permit the ignition spark gap to skip over between one electrode and the wall of the ignition chamber within the boundary layer. However, an increased leaning of the operational mixture and thus an increase in the wall temperature of the ignition chamber required for positive ignition, causes excessive overheating of the electrodes and glow sparking with subsequent thermal destruction of the electrodes. This is particularly true when the electrodes, in order to maintain the ignitability, are exposed directly to the fresh mixture flowing in and out of the ignition chamber or to the burned mixture at the entry of the transfer channel. Other possible solutions to the problem, which shift the ignition location to portions of the ignition chamber which are sufficiently remote from the entry point of the transfer channel can not, however, be operated with the desired degree of leaning or must be provided with a very expensive flushing system in order to free the ignition chamber sufficiently of hot remnant gases before it is supplied with fresh mixture.